1. Field of the Invention
The present invention relates to techniques for the characterization of treading surfaces.
2. Description of the Related Art
There exist various known techniques, some of which form the subject of specific standards, designed to enable the characterization of treading surfaces. These techniques have been developed, for example, for identifying, in a reasonably objective way, the characteristics of tread of surfaces such as, for example, floorings made of synthetic material.
These known techniques can be used also for the characterization of surfaces designed for practicing sports activities.
For instance, the standard DIN 18035/7 envisages specific criteria for measuring and calculating a parameter of absorption of energy KA (abbreviation of the German word Kraftabbau), which can be detected using an apparatus known as “artificial athlete of Berlin”. The requisites established by the International Federation of Football Association (FIFA) envisage that pitches for playing soccer will have values of KA comprised in the range between 55% and 70%.
The above DIN standard then envisages the possibility of measuring and calculating a parameter of standard deformation using another instrument commonly referred to as “artificial athlete of Stuttgart”. The FIFA requisites envisage a range of values between 4 and 8 mm.
Further useful information on the subject can be drawn from the European Standard published at the level of draft in October 2003 as prEN14808.
The “artificial athletes” considered above base their operation on a weight (i.e., a body of predetermined weight) sustained by a base structure resting on the surface to be characterized. The weight is dropped from a given height onto the surface, and associated to the structure is a cup sustained by a spring, which will be struck by the weight as it falls.
In other types of artificial athletes, it is envisaged that the weight will strike the surface to be characterized at the end of its fall: in this case the front face (or impact face) of the weight carries, however, a spring, to which a sensor device for detecting deformation is associated.
In the course of the last few years, synthetic grass floorings of the type described, for example, in EP-A-0 377 925, U.S. Pat. No. 4,337,283, U.S. Pat. No. 5,958,527, U.S. Pat. No. 5,976,645 or EP-A-1 158 099 have found an increasingly wide application.
The solution described in the document cited last enables reproduction in a highly faithful manner of the characteristics of tread and of response to mechanical stresses (bumps, impacts of various nature, etc.) of natural grass cover or turf.
In order to exploit this possibility fully, it is important to identify, in a precise and faithful way—and as objectively as possible—, the characteristics of a given natural grass cover and the characteristics of the synthetic grass flooring (turf) which is desired to be able to reproduce, with the greatest faithfulness possible the characteristics of natural grass cover, this both with specific reference to the biomechanical parameters that essentially determine the interaction of athletes with the surface of the flooring that they use and as regards, for example, the characteristics of bouncing of a ball used for practicing sport on said flooring.
The tests conducted in the course of the last few years demonstrate, however, that the methods and the instruments of characterization of a traditional type, such as those to which reference has been made in the introductory part of the present description, are unable to provide a particularly precise and faithful characterization of a surface, such as, for example, a grass cover, whether natural or synthetic.